Variation of glycine-activated conductivity of the membranes of spinal cord neurons in the chick embryo in culture

The method of leading off whole-cell currents is used to study the neuron responses elicited by applications of glycine at different stages of culturing of the chick embryo dissociated spinal cord. For two types of cells described earlier [4] differently directed shifts of the concentration dependence curves of the transmitter effect are shown to be characteristic. "Mature" cells, surviving several days in culture and represented by motoneurons, typically show a lowered sensitivity to glycine. The sensitivity of little-differentiated neurons increases more than tenfold by the end of the second week of culturing. The desensitization kinetics of the glycine-activated current also slows down with age. Blocking of the spontaneous electrical activity during development prevented these changes, and the presence of agonist in the culture medium did not affect them. Analogous patterns of formation of transmitter sensitivity are assumed to be exhibited by differentiating neurons of the intact nervous system.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 5, pp. 580–587, September–October, 1991.     

Synthesis and cytotoxic properties of anomeric 5-substituted 3'-azido-2',3'-dideoxyuridines]

Glycosylation of trimethylsilyl derivatives of 5-benzyloxymethyl- and 5-hydroxymethyluracil with 3-azido-2,3-dideoxy-5-O-benzoyl-D-ribofuranosyl chloride (prepared from ethyl 3-azido-2,3-dideoxy-5-O-benzoyl-D-ribofuranoside) and subsequent deacylation gave in both cases a mixture of anomeric 3'-azido-2',3'-dideoxy-5-benzyloxymethyl-or 5-hydroxymethyluridines. The anomers were separated by preparative TLC and their structures were studied by UV, IR and 1H-NMR spectroscopy. It is shown that 1-(3-azido-2,3-dideoxy-alpha-D-ribofuranosyl)-5-benzyloxymethyluracil has cytotoxic activity in vitro: in 10(-5)-10(-4) M concentrations it inhibits the thymidine incorporation into DNA of CaOv cells on 78.6-95.2%.     

Plants in urbanized natural environment: florogenesis,coenogenesis and population structure

Published data on both flora and phytocoenosis genesis and plant population dynamics are reviewed. Urbanized environment is rated as a stress factor for single plants and their communities. The change of plant population structure in cities and towns is analysed as the important indicator of the environment quality. The problems of phytoindication of environment quality in cities and towns for its optimization are considered.     

Variants in the interleukin-1 alpha and beta genes,and the risk for periodontal disease in dogs

Elevated levels of interleukin-1 (IL-1) have been shown to amplify the inflammatory response against periodontopathogenic bacteria. In humans, polymorphisms in the IL1A and IL1B genes are the most well-studied genetic polymorphisms associated with periodontal disease (PD). In contrast to human, there is a lack of knowledge on the genetic basis of canine PD. A case–control study was conducted in which a molecular analysis of dog IL1A and IL1B genes was performed. Of the eight genetic variants identified, seven in IL1A gene and one in IL1B gene, IL1A/1_g.388A >C and IL1A/1_g.521T >A showed statistically significant differences between groups (adjusted OR (95% CI): 0.15 (0.03–0.76), P= 0.022; 5.76 (1.03–32.1), P= 0.046, respectively). It suggests that in the studied population the IL1A/1_g.388C allele is associated with a decreased PD risk, whereas the IL1A/1_g.521A allele can confer an increased risk. Additionally, the IL1A/2_g.515G >T variation resulted in a change of amino acid, i.e. glycine to valine. In silico analysis suggests that this change can alter protein structure and function, predicting it to be deleterious or damaging. This work suggests that IL1 genetic variants may be important in PD susceptibility in canines.     

Inhibiting properties of stable nitroxyl radicals in reactions of linoleic acid and linoleyl alcohol oxidation catalyzed by 5-lipoxygenase

The inhibiting effects of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and its 4-substituted derivatives in reactions of linoleyl acid or linoleyl alcohol oxidation catalyzed by potato tuber 5-lipoxygenase were investigated. Inhibiting properties of stable nitroxyl radicals in presence of lubrol and SDS were reduced at the transition from TEMPO to 4-hydroxy-TEMPO or 4-amino-TEMPO and increased at use of adamantane-1-carboxylic or 3-methyladamantane-1-carboxylic acid 1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl esters. Enzyme activity at saturating concentrations of inhibitor was not suppressed completely, and decreased up to the certain level determined by the substrate nature. The dependence of partial inhibition efficiency on rotational correlation time of stable nitroxides in model micellar systems were analysed. It was supposed that 5-lipoxygenase inhibition includes the interaction of hydrophobic nitroxide with radical intermediate formed in enzymatic process.     

The difference between protein structures that are obtained by X-ray analysis and magnetic resonance spectroscopy

We have analyzed the proteins whose structures were determined both by X-ray analysis (X-ray) and nuclear magnetic resonance (NMR) on condition that these structures do not differ greatly when spatially superimposed on each other (61 pairs of protein structures). Atom-atomic contacts (contact distances varied from 2 to 8 A) have been analyzed and it has been found that NMR structures (in comparison with X-ray ones) have more contacts in the range below 3.5 A and above 5.5 A. In the case of residue-residue contacts NMR structures have more contacts below 3 A and between 4.5 and 6.5 A. At all the other contact distances analyzed the X-ray structures have more contacts. The difference in the number of atom-atomic and residue-residue contacts is greater for internal residues, that are concealed from water, as compared to the surface residues. The other, not less important difference deals with the number of hydrogen bonds in the main chain: it is larger for the X-ray structures. The correlation between the hydrogen bonds identified in the structures obtained by both methods is no more than 32%. The consideration of a complete set of protein structures obtained by NMR results in the fact that the number of hydrogen bonds grows 1.2 times as compared to those obtained with the X-ray analysis, whereas the correlation increases only by 65%. We have also demonstrated that alpha-helices in the NMR structures are more distorted in comparison with the ideal alpha-helix, than alpha-helices in the X-ray structures.     

Testing the quick meal hypothesis: The effect of pulp on hoarding and seed predation of Hymenaea courbaril by red‐rumped agoutis (Dasyprocta leporina)

Abstract: Red‐rumped agoutis (Dasyprocta leporina) are important seed dispersers/predators of Neotropical large‐seeded plants. Several species of seeds cached by agoutis have an edible reward, in contrast to temperate rodent‐dispersed diaspores. The quick meal hypothesis states that the presence of a reward such as edible pulp will enhance the efficiency of rodents as seed disperses by satiating the animal and, consequently, reducing seed predation and enhancing hoarding. In this study, this hypothesis was tested using as the reference system the pulp and seeds of Hymenaea courbaril. Seeds with and without pulp were offered to agoutis and the behaviour of each individual was recorded. Since the probability of predation and hoarding were complementary, we used the probability of predation. The proportion of agoutis that preyed on at least one seed was similar for seeds with (42.8% of individuals) and without (40.0% of individuals) pulp. In agoutis that preyed upon at least one seed, the probability that they killed a seed did not differ between seeds with (0.17 ± 0.03) and without (0.20 ± 0.08) pulp. Hence, these results do not support the ‘quick meal hypothesis’.     

Extrafloral nectaries as a deterrent mechanism against seed predators in the chemically protected weed Crotalaria pallida (Leguminosae)

Abstract In several plants, extrafloral nectaries (EFN) are located close to the reproductive structures, suggesting that ants may act as a defence against specialized seed predators that overcome chemical defences. Alternatively, ants may also deter herbivores in a generalized manner, thereby protecting the whole plant. In this work, we examined the relationship between the chemically protected weed Crotalaria pallida Ait. (Leguminosae) that bears EFN, its specialized seed predator, the larvae of the arctiid moth Utetheisa ornatrix L. (Arctiidae) and ants. We tested two hypotheses related to the type of deterrence caused by ants. The Seed Predator Deterrence Hypothesis predicts that ant deterrence is directed primarily towards herbivores that destroy seeds and other reproductive structures, without attacking herbivores on vegetative structures. The General Deterrence Hypothesis states that ants are general in their effects, equally deterring herbivores in vegetative and reproductive structures. Our results supported the predictions of the Seed Predator Deterrence Hypothesis, namely, that (i) ant activity on EFN was related to the vulnerability of reproductive structures to attack by U. ornatrix; (ii) ant patrolling was restricted almost entirely to racemes; (iii) ants removed termites used as baits more frequently on racemes than on leaves; and (iv) U. ornatrix larvae were often expulsed from the racemes. These results indicate that EFN can act as another deterrent mechanism in chemically protected plants by promoting the expulsion of specialist seed predators.